Abstract
Survival time of juvenile pen shell Atrina pectinata (shell length ≈ 34 mm) exposed to hyposaline water without sediments was investigated in laboratory experiments. The bivalves were individually maintained in rearing cups in which salinity was decreased either gradually (over 1–11 h to 12 salinities ranging from 0 to ca. 34 ppt) or rapidly (directly to 21 salinities) at 12 and 24 °C. When the environmental salinity was gradually decreased, survival time differed markedly between the bivalves exposed to: salinities ≤ 18.6 ppt (survival time < 20 h in general) vs. ≥ 21.1 ppt (> 83 h) at 24 °C; and between salinities ≤ 15.1 ppt (< 34 h) vs. ≥ 17.2 ppt (> 83 h) at 12 °C. When the environmental salinity was rapidly decreased, survival time, again, differed markedly between the bivalves exposed to: salinities ≤ 15.9 ppt (< 20 h in general) vs. ≥ 17.7 ppt (> 140 h) at 24 °C; and salinities ≤ 21.3 ppt (< 38 h in general) vs. ≥ 22.3 ppt (> 140 h) at 12 °C. Such sharp decreases in survival time due to reduced salinity led to the selected, statistical models that assume either a sharp exponential increase or stepwise hike in hazard (instantaneous mortality rate) according to salinity reduction. These data and models indicate that juvenile A. pectinata should not be kept at salinities < 21 ppt for periods > 1 day in environments without sediments.
Highlights
Salinity is one of major environmental factors determining the physiology and behavior of marine animals (Kinne 1966)
At both temperatures the survival time and expected LT50 of juvenile A. pectinata sharply decreased owing to a small decrease (\ 5 ppt) in salinity, as follows
Based on the previous and present experiments in which A. pectinata were exposed to low salinities with no sediment, it is possible to compare hyposaline endurance between juveniles vs. adults, 12 vs. 24 °C, and gradual vs. sharp decreases in salinity, as follows
Summary
Salinity is one of major environmental factors determining the physiology and behavior of marine animals (Kinne 1966). In shallow seas salinity changes owing to various factors (e.g. tidal currents, terrestrial runoff, rain). Such changes often lead to the mortality of various. The influence of salinity changes on survival has been studied for a diverse range of animals (Newell 1976) These studies include hyposaline endurance of marine bivalves The studies on bivalves revealed that their endurance of hyposaline conditions depends on various factors including species specificity, life stage, temperature, and the rate of salinity change. High or low water temperature leads to lowered hyposaline endurance in some species (Chlamys opercularis, Mytella charruana, Perna viridis; Paul 1980; Yuan et al 2016). More rapid decreases in salinity possibly lead to lower hyposaline endurance, since some bivalves cannot change the densities of osmolites in their cells quickly enough (Shumway et al 1977)
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